Opportunity Sol 723 (Spirit Sol 743)

Yestersol I came in with Matt Heverly and Frank Hartman to take a look at the RP-0 sequences Jeng and Ashitey had put together for thisol. To our astonishment, they'd decided to send up the previous sol's sequences despite wrist-flip problems -- which can cause the sequence to fault out, if you're even a little unlucky -- and their RP-0 sequences had the same problem. Yestersol's sequences worked fine, but Frank and I are of one mind that thisol's need to be fixed.

However, despite our needing to make some small changes to both the IDD and drive sequences, the draft versions save us a lot of time and stress. More than enough for me to start putting together canned stow, unstow, and rotor-resistance-setting sequences for us to use in our new stow/drive/unstow driving routine. (To my annoyance, we decide not to uplink these sequences on this sol, because we haven't yet figured out how we're going to safely deactivate them if they should run unusually long. But I get them built, anyway.)

Martian winter is setting in. One of our first signs of it is longer heating times required in the drive sequences, after which we tell the spacecraft to expect colder temperatures despite the heating. And, Bill Nelson points out, we're no longer in a relatively warm crater, as we were last winter; we're out on the chillier plains. This is bad news for Opportunity's Mini-TES, which is especially vulnerable to the extra-cold temperatures it experiences when we must Deep Sleep to conserve power. They call Squyres to ask him about this -- should we curtail activities to avoid Deep Sleeping, or accept the additional risk? "Take the risk," is his call. You can hear the shrug. "We made this decision basically one Martian year ago." If we lose the MTES, we lose it -- although that would truly suck on a rover that already has a failing IDD. If the IDD and the MTES both go, we're left with only the PCAM for science instruments.

The power loss has another implication: we'll have to Deep Sleep nightly, meaning we'll have fewer comm passes, meaning we'll get less data daily. (If we won't have any science instruments to return data from, that's not so bad. I didn't just say that.) Frank's been asked to put together a scheme for driving with only 40 Mbits of downlink per sol, which I would have thought unlikely until he shows me the scheme. It'll be tight, but I think we can do it -- and oddly enough, I think this will help focus us on driving. We'll get to a point where we can't afford to do anything else.

Speaking of driving, John Callas stops in to pick my brain about strategies for driving more meters per sol on the way to Victoria, which NASA HQ is now apparently starting to push hard for. I talk about the same stuff with him as I have with Frank -- using autonav, lengthening the distance between slip checks, and so on.

But the big thing, I tell him, is to get the scientists pushing for driving. And the only demonstrated way to do that is with a drive metric: pick a sol, and say we're going to be there by that sol, and keep putting our progress (or lack of it) up on the board every day for all to see. This doesn't work perfectly; the scientists will spend on credit. And sometimes, as with Spirit, there isn't enough margin left, and we don't get to Home Plate on time. Not that I'm bitter. But it works well enough, all the same.

The odd part of this conversation comes when John reveals that he's a bit of a train nut. "Oh, if my dad ever comes out for a visit, I'll have to introduce you," I tell him. "He was an engineer for CSX transportation -- retired just a year or so ago."

John's eyes light up like a little kid's. "When is your dad coming for a visit?" he asks eagerly.

A visit from one project manager just wouldn't be enough. Our sadly-soon-to-be-ex-project manager, Jim Erickson, also pops by. He's already splitting his time, and soon he'll be gone from MER for good. Julie asks him how things are going.

"Okay," he says.

"Just okay?"

He shrugs. "It's much less fun to do two things badly than to do one thing well," he says.

[Next post: sol 746, February 7.]